Used primarily as an intermediate in organic synthesis, especially in the production of pharmaceuticals and fine chemicals. Its cyclic structure and reactive anhydride groups make it valuable for constructing complex molecules, including active pharmaceutical ingredients where ring systems are needed. It is also employed in the development of specialty polymers and resins, contributing to enhanced thermal and chemical resistance. Due to its ability to form esters and amides readily, it serves in modifying functional groups during multi-step syntheses.